PARIS (Reuters) - Several European countries have reported outbreaks of a severe strain of bird flu, the World Organization for Animal Health said on Thursday, while France raised safety checks to counter the virus which can have a major impact on farmers.

The World Health Organization for Animal Health (OIE) said Germany, Austria, Croatia and Switzerland had all officially reported the outbreaks, which concerned a particularly virulent strain affecting wild birds.

France's Agriculture Ministry added in a statement that the highly pathogenic H5N8 virus had been found in wild birds in Hungary, Poland, Germany, Croatia, the Netherlands and Denmark.

Austria and Switzerland on Thursday took precautionary steps to prevent the spread of bird flu to domestic poultry after discovering cases of the disease in wild ducks around Lake Constance.

The Dutch government took similar steps earlier this week, when it ordered farmers in the Netherlands to keep poultry flocks indoors following the outbreak of the virus.

Though the H5N8 virus is highly contagious in birds, it has never been found in humans.

It had been found in several European Union countries in 2014 and led to massive poultry cullings.

France, the European Union's largest agricultural producer, had at one stage imposed stricter controls and banned duck and goose production in 17 administrative departments, to contain an earlier outbreak of the bird flu virus.

(Reporting by Sybille de La Hamaide, Editing by Mark Potter and Elaine Hardcastle)